The present disclosure relates to an image forming apparatus preventing a curl from occurring in a sheet conveyed through a fixing part, a first conveying part and a second conveying part.
An image forming apparatus, such as a printer, a copying machine and a facsimile device, heats and melts a toner of a toner image formed on a sheet, such as a printing paper, and fixes an image onto the sheet by further heating. To the sheet, an upward curl or a downward curl may be applied by various factors, such as a load caused in transferring the toner image, a load caused in fixing and a load caused in conveying. Particularly, infixing, because the sheet is heated and moreover pressured, the curl easily occurs in the sheet. The curl occurs remarkably in an end part at an upstream side and an end part at a downstream side in a conveying direction of the sheet. This curl causes a jam due to conveying failure, a stacking failure of the sheet after ejection and others to occur. Therefore, conventionally, it is proposed to restrain the curl occurring in the sheet. For example, the image forming apparatus restraining the curl by quickening conveyance of the sheet after fixing to warp the sheet to an opposite direction to a curl direction in a curved shape is proposed.
However, in a conventional mechanism, because the warp of the sheet passed through a fixing part is not stabilized, dispersion of a contact time of a sheet surface with a heating roller occurs, and then, it is feared that a fixing property of the image onto the sheet is not stabilized. In addition, as a result of the dispersion of the contact time, it is feared that dispersion of glossiness in the conveying direction occurs in the image of the sheet and the image cannot be taken uniformly.